1. Field of the invention
The present invention relates to a process for solid-phase bonding ceramic bodies and the thus produced bonded articles.
2. Description of the Related Art
The present inventor disclosed a ceramic heater as described below as a heating apparatus for use in a thermal CVD apparatus for producing semiconductors, for example in a specification of Japanese patent application 301,897/1991. For producing such ceramic heaters, it is necessary to bond a disk shaped base made of silicon nitride sintered body having a heat resistor made of tungsten therein and a tube shaped body made of silicon nitride for preventing the leakage of a corrosive gas or a gas for forming semiconductor films. However, the inventor found it difficult to form strong and gas-tight bonding between the base and the tube shaped body. For example, the inventor tried to bond the disk shaped base and the tube shaped body to obtain the heating apparatus (a bonded article) using a glass adhesive made of an oxide glass. However, a mechanical strength of the bonding interface of the bonded article was low. Moreover, when such heating apparatus was placed in an apparatus for producing semiconductors and the gas for forming semiconductor films or the corrosive gas was supplied and flowed into the semiconductor producing apparatus, gas leakage may occur at the bonding interface of the base and the tube shaped body. Additionally, cracks may occur along the bonding interface when using the heating apparatus repeatedly.
As described above, the inventor conducted intensive research for producing a bonded article of ceramic bodies made of silicon nitride or aluminum nitride with a high mechanical strength. However, because of several reasons including high sintering temperatures of the ceramic bodies, the inventor failed to find an appropriate process for such bonding in prior art processes. For example, the inventor tried to apply a powdery bonding agent between the ceramic bodies which is then heated to diffuse ingredients of the powdery bonding agent. However, it was difficult to produce the bonded article with a high mechanical strength and gas-tight performance at the bonding interface.